Energy Balance Definition

Thus, if the total energy contained in the body (as fat, protein, and glycogen) is not altered (i.e., A energy stores = 0), then energy expenditure must be equal to energy intake. In this case, the individual is said to be in a state of energy balance.

If the intake and expenditure of energy are not equal, then a change in body energy content will occur, with negative energy balance resulting in the utilization of the body's energy stores (glycogen, fat, and protein) or positive energy balance resulting in an increase in body energy stores, primarily as fat.

The difference between the concepts of energy balance and heat balance is presented in Figure 1.

Model of Energy Balance: A Dynamic State

There are multiple reciprocal direct and indirect influences of energy intake on energy expenditure and vice versa: for example, energy intake influences

resting energy expenditure by increasing postprandial and dietary-induced thermogenesis, whereas changes in energy expenditure via a modification of physical activity is susceptible to influence energy intake to maintain energy balance. In order to assure an accurate regulation of body stores, a double control is essential (see below). Body weight and body composition are not invariant with time but small corrections of both input and output from day-to-day or week-to-week, assure energy homeostasis (Figure 2). When attempting to explain the actual responses in energy balance and weight regulation in real life, we need to recognize that several factors may be operating at once on both sides of the energy balance equation. Compensatory adjustments occur in both intake and output, so unravelling the importance of one or other adjustment is not easy in man.

Many women who have recently given birth are always interested in attempting to lose some of that extra weight that traditionally accompanies having a baby. What many of these women do not entirely realize is the fact that breast-feeding can not only help provide the baby with essential vitamins and nutrients, but can also help in the weight-loss process.